Air blast attenuators and ventilators in the past have been constructed in the form of valves that include moving valve members. The structure is arranged so that the valve members move in response to the blast to shut off the attenuator valve. Such valves were primarily designed for use in connection with nuclear blasts and were arranged to provide adequate ventilation when the valve is open. When the valve senses the blast and closes, it will attenuate blast effects where the effects occur over a long period of time. However, such valves have not been effective where the air blast is a result of a detonation of a conventional weapon such as a high explosive bomb. The duration of the air blast is so short in such explosions that the valve mechanisms do not have time to respond and close to attenuate the blast effects.
In response to this difficulty, passive air blast attenuators have been developed and are constructed of items such as nested I-beams, nested angles and zees which provide tortuous flow paths which impede or attenuate the blast effects upon detonation of high explosives. However, such structural arrangements do not provide for adequate ventilation due to the high pressure drop of ventilation gas flowing therethrough.
Accordingly, a substantial amount of work has been done with various arrangements of ported plates in an effort to provide both air blast attenuation and ventilation. Such devices are described in detail in a report entitled "Passive Air Blast Attenuation Valves for Conventional Weapons". This report was prepared for the U.S. Army Engineer Waterways Experiment Station by Quentin A. Baker, et al. The report is Report No. WBE-124, dated Oct. 31, 1989 and was prepared under Contract No. DACA39-89-C-0035.
The ported plate type attenuators described in that report were reasonably effective in attenuating the blast effects while at the same time providing for adequate ventilation. However, it is highly desirable to provide a greater degree of blast attenuation while at the same time providing for better ventilation. The attenuators and ventilators discussed herein are used for preventing insofar as possible any blast effects from passing into a building, occupied either by equipment or personnel, and at the same time being able to provide adequate ventilation. Also, such devices may be utilized in a munitions facility, arsenal, hazardous material manufacturing facility, or chemical processing facility to prevent blast effects from escaping a room where such explosives or flammable materials are stored or manufactured should an accidental explosion occur and also to provide ventilation for the structure.
Our further object is to provide in such attenuators and ventilators effective to attenuate the effects of a blast and providing ventilation that is easily constructed, has no moving parts, is of low cost, and is easily maintained.